The present invention relates to a washing machine comprising a drum and a heat pump system for heating water fed to said drum in a washing program of the machine, the heat pump system having an evaporator in heat exchange relationship with air flow and a condenser in heat exchange relationship with said water.
Washing machines using a heat pump system for heating up water are known in the art, for instance form JP 2010069194. These machines have high energy efficiency since during the heating phase a big amount of energy is required to warm up the water, and the use of a heat pump system allows reducing substantially the amount of energy required during this phase. It is possible to implement a heat pump that with a limited amount of energy absorbed from the mains is capable to deliver an amount of heat from 3 to 6 times bigger as heat.
CN102286872 discloses a heat pump laundry dryer which can carry out either a normal drying cycle in which the process air is re-circulated across the evaporator and the condenser of the heat pump system and in the drum, or an ambient room dehumidification cycle where two flaps are placed downstream the exit of air flow from the drum and upstream the entrance of air flow in the drum respectively, so that ambient air is passed though the evaporator and condenser in order to reduce the humidity thereof, and that such dehumidified air is fed back to the ambient. Such solution is quite complex since two diverters or flaps have to be used in the air circuit. Moreover the dehumidification configuration of the dryer can be adopted only when the dryer has finished the drying process. Since a closed-loop heat pump dryer does not emit vapor in the ambient room (humidity is condensed in the evaporator and removed as liquid water), after the drying cycle there is usually no need to reduce the humidity in the ambient air.
On the contrary, washing machines are often installed in small rooms (bathroom or laundry room) and once the washer cycle is ended, the laundry is normally dried using a clotheshorse. As a consequence, the air humidity in the bathroom or laundry room will increase annoying the customer. It is known that at home there is an ideal range of relative humidity, i.e. from 40% to 75%, and that upper end of the range can be easily over passed in rooms where clothes are placed for drying, leading even to possible water condensation on cold surfaces as windows.